1. Field of the Invention
The present invention relates to an adhesive material for connecting a protuberant electrode of a semiconductor element or the like to a terminal electrode of a circuit board for carrying said electronic component.
2. The Description of the Related Art
IC packages in which semiconductor elements are mounted on packaging substrates which have a relatively larger surface area than the semiconductor element have conventionally been mounted on motherboards in portable electronic devices, e.g., cellular telephones. Recently, however, there has been a trend towards lighter, thinner, shorter and smaller electronic devices as well as towards increased functionality.
Accompanying this trend there has been a practice of flip-chip mounting the semiconductor element itself on the motherboard in a bare-chip state and a use of chip size packages (CSP) which have been mounted on packaging substrates which are roughly the same size as the semiconductor element, in place of the conventional IC package. In such cases, an insulating adhesive in the form of a liquid, paste or film, or an anisotropically conductive adhesive in the form of a paste or film, in which conductive particles are dispersed in these insulating adhesives, are used when the protuberant electrode (bump) of the bare chip or CSP is to be connected to the terminal electrode of the motherboard.
Stress becomes concentrated in the protuberant electrode of the bare chip due to the difference in thermal expansion coefficient between the motherboard and the bare chip (or CSP) in the portions where connections are made by using such adhesives. This leads to the drawback of the protuberant electrode frequently separating or peeling away, which causes the conductivity resistance to increase, poor connections to be formed, and the reliability of the connections to be markedly diminished.
Moreover, scatter in the heights of the bare chip protuberant electrodes also leads to scatter in the distances between the motherboard connecting terminals and the corresponding bare chip protuberant electrodes. This leads to the drawback that the reliability of the connections shall not improve.
Accordingly, it has been proposed that in order to ensure the reliability of the connection between the motherboard and the bare chip, an inorganic filler with a mean particle size of 3 microns or less should be compounded with the insulating adhesive or anisotropically conductive adhesive at a ratio of 5 to 200 wt pts per 100 wt pts adhesive resin composition, to increase viscosity and improve adhesive strength (Japanese Patent Application Laid-Open No. (HEI) 11-061088).
However, as disclosed in Japanese Patent Application Laid-Open No. (HEI) 11-061088, sufficient reliability in the adhesion between the motherboard and the bare chip cannot be assured, if the inorganic filler particle size and compounding amounts are merely specified.
With the foregoing problems of the prior art in view, it is an object of the present invention to eliminate any scatter in the distance between a protuberant electrode of a semiconductor element or the like, and a terminal electrode of a motherboard or other circuit board, while enabling the connections to be satisfactorily reliable.
The present inventors perfected the present invention based on the discovery that the aforesaid object can be achieved when connecting a protuberant electrode of a semiconductor element or the like to a terminal electrode of a circuit board for carrying said electronic component, through an adhesive material that contains at least one curable resin and inorganic particles, not solely by determining the mean particle size and compounding amount of the inorganic particles used, but by establishing the specific surface area of the inorganic particles within a prescribed range, and establishing the maximum particle size at one half or less of the sum of the height of the protuberant electrode on the electronic component and the height of the terminal electrode of the circuit board.
In other words, the present invention provides an adhesive material for connecting a protuberant electrode of an electronic component (preferably a bare chip or another semiconductor element) to a terminal electrode of a circuit board for carrying said electronic component through the adhesive material containing at least one curable resin and inorganic particles, said adhesive material being characterized in that as to the inorganic particles, their specific surface area S (m2/g) satisfies Equation (1) below, their mean particle size D1 (xcexcm) and maximum particle size D2 (xcexcm) respectively satisfy Equations (2) and (3) below,
3 less than Sxe2x89xa617xe2x80x83xe2x80x83(1)
D1xe2x89xa65xe2x80x83xe2x80x83(2)
D2xe2x89xa60.5(h1+h2)xe2x80x83xe2x80x83(3)
(wherein h1 represents the height of the protuberant electrode in the electronic component, and h2 represents the height of the terminal electrode in the circuit board), and the content of said inorganic particles is 10 to 60 vol %.
Furthermore, the present invention provides a circuit connection method, in which a protuberant electrode on an electronic components that contains said protuberant electrode (preferably a bare chip or another semiconductor element) is connected to a terminal electrode of a circuit board for carrying said electronic component through an adhesive material containing at least one curable resin and inorganic particles, said circuit connection method being characterized in that an adhesive material in which inorganic particles whose specific surface area S (m2/g) satisfies Equation (1) below and whose mean particle size D1 (xcexcm) and maximum particle size D2 (xcexcm) respectively satisfy Equations (2) and (3) below
3 less than Sxe2x89xa617xe2x80x83xe2x80x83(1)
D1xe2x89xa65xe2x80x83xe2x80x83(2)
D2xe2x89xa60.5(h1+h2)xe2x80x83xe2x80x83(3)
(wherein h1 represents the height of the protuberant electrode in the electronic component, and h2 represents the height of the terminal electrode in the circuit board) are dispersed in a curable resin in an amount of 10 to 60 vol %, is used as the adhesive material.